Predictors of Diagnostic Variables of Sarcopenia in Older Adults

Abstract

PURPOSE: To investigate potential predictors of diagnostic variables of sarcopenia in older adults including demographic factors (e.g., age and sex), aerobic and resistance physical activity (PA), cardiorespiratory fitness (CRF), and body composition. METHODS: This cross-sectional study included 304 older adults ≥65 years (mean age 73, range 65-95). PA and sedentary variables were assessed using a self-report survey and daily steps using an accelerometer based pedometer (Omron HJ-321). CRF was the time to complete a 400m walk in minutes, thus higher number in minutes indicates a slower walking, which is a lower level of CRF. Body composition was percentage body fat (%BF) measured by DXA and body mass index (BMI). Diagnostic variables of sarcopenia include appendicular lean mass (ALM) (kg/height in meter2) measured by DXA, handgrip strength (kg), and gait speed (m/s) from 4 meter walk test. RESULTS: Univariate regression revealed significant relationships between ALM and CRF (p=0.012), light intensity (1.5-3.0 METs) aerobic PA (p<0.001), vigorous intensity (≥6.0 METs) aerobic PA (p=0.008), age (p<0.001), male sex (p<0.001), and %BF (p<0.001). Handgrip strength was related to CRF (p<0.0001), light intensity aerobic PA (p=0.002), vigorous intensity aerobic PA (p=0.002), resistance PA (p=0.031), age (p<0.001), male sex (p<0.001), and %BF (p<0.001). Gait speed was related to CRF (p<0.0001), daily steps (p=0.003), age (p<0.0001), and %BF (p=0.018). Stepwise variable selection (p<0.2 to enter the model, p<0.05 to remain in the model) was used to find significant predictors of diagnostic variables of sarcopenia. ALM was predicted by CRF (β=-0.15, p<0.001), %BF (β=-0.12, p<0.001), BMI (β=0.25, p<0.001), and male sex (β=0.29, p<0.001) (model R2=0.93); grip strength was predicted by CRF (β=-2.50, p<0.001), age (β=-0.26, p<0.001), and male sex (β=14.6, p<0.001) (model R2=0.63); and gait speed was predicted by CRF (β=-0.11, p<0.001) (model R2=0.24). CONCLUSION: Cardiorespiratory fitness, measured by a simple 400m walk test, was identified as a significant predictor of all three diagnostic variables of sarcopenia in older adults.